Physical, Chemical and Geotechnical Characterization of Wet Flue Gas Desulfurization Gypsum and Its Potential Application as Building Materials

Abstract

In South Africa, coal represents the primary source of energy used for electricity generation. Coal power plants use the wet flue gas desulfurization (WFGD) process to remove sulfur dioxide (SO2) from their flue gas. However, this technology produces a large amount of synthetic gypsum, resulting in waste disposal and environmental pollution. This study investigated the physical, chemical and geotechnical properties of WFGD gypsum and its potential application to develop cement-free bricks. WFGD gypsum was collected from a coal power plant in South Africa. It was found that the principal oxides of WFGD gypsum were sulfur trioxide (SO3) and calcium oxide (CaO), which represented more than 90% of the total weight. Calcium sulfate (CaSO4) and calcium di aluminate (CA2) were the predominant minerals in the raw material. The density of the WFGD gypsum was 2.43 g/cm3. The maximum dry density and optimum moisture content values were 1425 kg/m3 and 18.5%, respectively. WFGD gypsum had a liquid limit of 51% but did not display any plasticity characteristics. The optimum curing temperature of gypsum bricks was 40 °C. WFGD gypsum-based bricks exhibited compressive strength of up to 2.3 MPa and a density of about 28% less than that of typical clay bricks. Additionally, there was no significant decrease in compressive strength after seven wet/dry cycles. These results show that WFGD gypsum could be used to produce lightweight building materials with low strength requirements.

Application of the Industrial Byproduct Gypsum in Building Materials: A Review

“…As the content of CaSO 4 •2H 2 O in the industrial byproduct gypsum usually reaches 70%, its CaO and SO 3 contents are more than 70%, and the remainder contains a small amount of SiO 2 and Al 2 O 3 [1,28]. Various forms of gypsum may contain distinct impurities.…”

“…The industrial byproduct gypsum refers to the byproduct or waste residue generated by chemical reactions in industrial production with calcium sulfate as the main component. It is also known as chemical gypsum or industrial waste gypsum, and the main component is calcium sulfate dihydrate (CaSO 4 •2H 2 O) [1]. According to the output industry and species, the industrial byproduct gypsum mainly includes desulfurization gypsum, phosphogypsum, titanium gypsum, citrate gypsum, fluorogypsum, and salt gypsum.…”

Mechanical Properties and Mineral Characteristics of Multi-Source Coal-Based Solid Waste Filling Materials under Different Proportioning

“…However, when the content of DG increased to 80%, the compressive strength of Specimen S-5 (20% PC, 80% DG) at any given curing age had no further growth but rather a slight decrease compared to that of Specimen S-4 (40% PC, 60% DG), indicating that once DG content exceeds 60%, C-S-H formation cannot be further promoted. Thus, the precipitation, crystallization, and growth of gypsum are severely hindered [31]. Therefore, the addition of DG cannot only reduce the PC amount and preparation cost, but also improve the compressive strength.…”

Mechanical Properties and Coagulation Characteristics of Flue Gas Desulfurization Gypsum-Based Polymer Materials

“…The above studies have identified promising ways to utilize the resource of FGDG. However, most of them are limited to using FGDG either as retarder or mineral additive, the safe consumption of which is low, thus preventing its large-scale application [ 15 ]. FGDG is a calcium sulfate mineral with potential as a raw material for the preparation of polymer materials [ 16 ].…”